The Apple Store in Grand Central Station. Source: Apple.

There's no shortage of reports coming out about Apple's (AAPL 1.27%) upcoming smartwatch, and The Wall Street Journal and Reuters added some fuel to the fire this week with their latest details on a possible iWatch launching this fall.

Based on the WSJ report, and a new one from Reuters, here's what we know so far:

Size and sensors
Apple is likely to release more than one size for the iWatch, considering that one of the biggest criticisms of current smartwatches is that they take a one-size-fits-all approach. However, Reuters is saying the screen size will be 2.5-inches and have a slightly rectangular display. The screen is expected to come from LG Display, and rise slightly up from the watch.

If Apple wants to differentiate itself from the current smartwatch competition, different sizes will be a must. Wearable tech is as much a fashion statement as it is functional gadgetry, and selling millions of smartwatches will likely require offering customers different size options.

Inside the watch will be 10 sensors, with much of the focus concentrating on using Apple's Health app. One such sensor is expected to be a pulse monitor, supplied by Heptagon. 

Who, when, and how many sales
Manufacturing is expected to begin in July, with 70% of it coming from Taiwan-based Quanta Computer. Quanta currently builds the Mac and iPod for Apple. According to some reports Apple is still finalizing the details of the watch, but expects to launch sometime in October.

Both reports gave estimates for iWatch sales, with WSJ saying 10 to 15 million would be sold by the end of this year, and Reuters saying 50 million would be sold within the first 12 months after launch. But as with any new product launch estimates, no one really knows.

Though an iWatch is clearly a huge opportunity for Apple, I think the company has some substantial hurdles it'll have to overcome for the watch to be a mass-market success. The two biggest issues will be design and pricing. The device will be on the wrist of users every day, and there's no room for bulky tech gadgetry for the masses. This device will have to be one of Apple's sleekest designs ever.

If Apple gets that right, then pricing will be the next factor. Analysts have pegged the device anywhere between $250 and $350, but with the smartwatch market so unproven (despite the current competition) it's hard to know where the sweet spot is between offering lots of features and pricing it where millions of people can afford it. With the initial launch of the iPad, Apple talked up the features then revealed a price that came in much lower than people anticipated -- it would be wise to take the same approach this time.

Foolish thoughts
As with most rumors, some of this is probably true but it's not likely all of it is. The upside for investors is that we know Apple Chief Executive Officer Tim Cook has committed to entering new product categories before the year's end, and with all these iWatch rumors, and the launch of HealthKit earlier this month, it's very plausible Apple will bring a smartwatch to market this fall.

Though Apple's opportunity in the wearable tech space is huge, I'm taking a cautiously optimistic approach to the device. Not because I don't think Apple can get the product right, but because I'm still slightly skeptical the mass market is ready to shell out hundreds of dollars for such a device.